Effects of Creatine Loading on Rowing Performance in Male Competitive Rowers / 体力科学

The purpose of this study was to investigate the effects of creatine loading on rowing performance in well-trained male competitive rowers (age 19.4±0.2 yr, height 182.2 ± 1.2 cm, weight 76.6±1.1 kg, mean±SE) . Twenty subjects were randomly separated into creatine (n=10) or placebo group (n=10) . Subjects performed simulated 2000 m rowing race and 20 sec maximal rowing on a rowing ergometer, before and after 6 days of creatine (20g of creatine monohydrate plus 4g of lactose per day) or placebo (24g of lactose per day) ingestion, The creatine and placebo were administered in a double-blind research design. Performance time for 2000 m rowing was improved significantly from 407.9±5.3sec to 404.7±5.4sec (p<0.01) in the creatine group, but no significant changes were observed in the placebo group. No significant changes were observed in power output during 20 sec maximal rowing in either groups. These results suggest that creatine loading can enhance performance in simulated 2000 m rowing race in well-trained competitive male rowers but has no beneficial effect on 20 sec maximal rowing.

Prevalence of disordered eating patterns and menstrual status in japanese female athletes / 体力科学

This study investigated the desire and its reasons for weight loss, the prevalence of disordered eating patterns and menstrual status, by using written questionnaires and Eating Attitude Test-26 (EAT-26), in Japanese female athletes (n=1000) and nonathletic controls (n=593) . Athletes were divided into the following 6 categories : technical (n=84), endurance I (n=84) and II (n=76), aesthetic (n=120), ball-game (n=447), and power sports (n=189) . Endurance I consisted of athletes competing in sports where leanness were considered important, while endurance II consisted of athletes competing in sports where leanness is less important. In each category, about four fifths of the athletes wanted to reduce their present weight. As to the reasons for weight loss, the athletes, especially those in the categories of endurance I (79%), power (52%) and aesthetic (34%) sports, reported that they prefer to be thin for improving their athletic performance. The prevalence of disordered eating patterns estimated by EAT-26 was significantly higher (P<0.05) in the athletes of endurance I (20%) and aesthetic (12%) groups than in the nonathletic controls (3 %) . In the athletes of these two sporting event categories, higher rates of amenorrhea (endurance I 20% and aesthetic 7 % vs. nonathlets 1 %) were found to be accompanied by lower values of obesity index and BMI. These data indicate a significantly higher prevalence of disordered eating patterns and menstrual dysfunction in the athletes involved in sports where leanness is emphasized, and a close relationship among undernutrition, low body weight and menstrual dysfunction.

Relationship between maximal aerobic power and the fatiguability during repeated isokinetic contractions / 体力科学

To investigate the relationship between maximal aerobic power (VO<SUB>2</SUB>max) and fatigu-abililty during repeated isokinetic contractions, 39 male speed skaters (mean 20.8 years) served as subjects. They were divided into two groups according to their VO<SUB>2</SUB>max levels ; high VO<SUB>2</SUB>max group (HI, n=19) and low VO<SUB>2</SUB>max group (LO, n=20) . VO<SUB>2</SUB>max was measured in all subjects during incremental exercise on a bicycle ergometer and body composition was determined by densitometry. Cross-sectional area (CSA) of the leg extensor muscles was evaluated using ultrasonic method. Fatiguability was assessed during the fatigue test consisting of 50 repeated isokinetic knee-extensions at an angular velocity of 180 deg⋅sec<SUP>-1</SUP>. Remark-able findings include :<BR>1. There were no significant differences in body composition and thigh composition between the two groups except for high subcutaneous fat in group LO.<BR>2. There were significant differences in VO<SUB>2</SUB>max between group HI (3.93<I>l</I>⋅min<SUP>-1</SUP>, 67.3 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) and group LO (3.59<I>l</I>⋅min<SUP>-1</SUP>, 59.9 m<I>l</I>⋅kg LBM<SUP>-1</SUP>⋅min<SUP>-1</SUP>) .<BR>3. In the fatigue test, the average initial values did not differ, however, the average final values were higher in group HI. Also, a significant difference was observed in per unit CSA between the two groups.<BR>4. Higher peak forces (kg) in group HI were observed after the initial 30 dymanic contractions per unit CSA and % of peak values (% peak force) .<BR>5. A close relationship was demonstrated between VO<SUB>2</SUB>max per LBM and the fatigue index, i. e., the mean decline in peak force with 50 contractions (r=-0.37, p<0.05) .<BR>Based on the present findings it is suggested that maximal aerobic power (VO<SUB>2</SUB>max) influences the rate of fatigue development even during short-term maximal isokinetic contractions, and that there may be some physiological cross-linkages between cardiopulmonary regulation and the metabolic properties of skeletal muscles. This finding is also in conformity with earlier results indicating the importance of oxygen delivery as a limiting factor for muscle performance.